<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>

        div{
            width: 100px;
            height: 100px;
        }

        .red{
            float: left;
            background-color: red;
        }

        .green{
            background-color: green;
            /* float: left; */
            width: 300px;
            height: 300px;
        }
        .biue{
            background-color: blue;
            /* float: left; */
           
        }

    </style>
</head>
<body>
    <div class="red"></div>
    <div class="green"> 大家好</div>
    <div class="biue"></div>
</body>
</html>